Packaging material is manufactured through fold forming, thermo-forming or other mechanical treatment for shaping of a strip or a prefabricated substance of flexible packaging material. For the purpose of making the packaging container easy to open, a tearing mark is incorporated in the container wall, the tearing of which entails that a part of the wall delimited by the tearing mark can be pulled up or torn off completely to expose a corresponding opening through which the packaging container can be emptied of its contents.
Within packaging technology finished consumer packagings of disposable character have long been used which are made of a laminated, flexible packaging material containing one or more skeletal layers of paper or cardboard and outer layers of plastic, usually polythene. These so-called disposable packagings are now most frequently produced with the aid of rational, modern packaging machines of the kind that both shapes, fills and closes the packagings on a large industrial scale.
From, for example, a strip of the packaging material of such a disposable packaging is produced through the strip first being shaped into a tube through the two longitudinal edges of the strip being joined to each other in a longitudinal overlap joint. The tube is filled with the contents and divided up into closed, filled packaging units through repeated transverse sealings of the tube across the longitudinal direction of the tube below the level of contents of the tube. The cushion-shaped packaging units are separated from each other through cuts in the transverse sealing zones and are given the desired, usually parallelepiped shaped final form through a final shaping and sealing operation during which the two upper triangular, double-walled corner flaps are folded down against and sealed to adjacent, opposite sides of the packaging and the two lower triangular, double-walled corner flaps are bent inwards towards and sealed to the bottom end of the packaging. A well known example of such a parallelepiped shaped disposable packaging is Tetra Brik (reg. trade mark) which is used for packaging and transporting among other things liquid foodstuffs such as milk, juice, wine etc.
Another well known example of a disposable packaging of the type described above is Tetra Top (reg. trade mark) which is also used for packaging and transporting among other things liquid foodstuffs such as milk, juice etc. This known disposable packaging is manufactured from a prefabricated substance of a paper or cardboard based packaging material through the substance first being shaped into a tube through the two opposite sides of the substance being joined to each other in a longitudinal overlap joint. One open end of the tube (corresponding to the top part of the packaging) is closed with the aid of a plastic lid which is injection moulded in place at the end of the tube. The tube is then filled with desired contents and is closed through fold forming of the end parts of the tube to form a bottom closure of the same type as in the above described type of packaging.
The requirement set for disposable packagings and packagings in general is of course that they must give the best possible mechanical and chemical protection to the product that is to be packaged, but also that they must be easy to open without implements, e.g. scissors, and that the contents of the packaging must be able to be poured out in a collected and well directed stream through the opening in the packaging.
In order to fulfill the requirement for good opening and pouring properties the known packagings are most frequently provided with some type of opening device, e.g. a tearing mark incorporated in the packaging wall as described in Swedish patent 344 725. This opening device which preferably appears on disposable packagings of the type Tetra Brik can, as described in Swedish patent 344 725, consist of a perforated tearing mark applied to one upper corner flap of the packaging, extending around the whole corner flap in an area between the tip and the base line of the corner flap (corresponding to one side of the top of the packaging). The packaging is opened through the corner flap being pulled away and bent upwards from its downward facing sealing position against the adjacent side of the packaging, after which the part of the flap situated outside the perforated tearing mark is gripped and torn off completely through the breaking of the perforated tearing mark which goes around it, so as to expose a pipe-shaped opening through which the packaging can be emptied of its contents.
An opening device of this kind is simple and easily manufactured and does not require any complicated separate equipment for its manufacture, but often produces an uneven, frayed tearing edge around the contour of the opening which impairs the desired collected and well directed stream. The problem is further aggravated by exposure of the fibrous material in the skeletal layer all around the contour of the opening to liquid. The material easily absorbs liquid and after a relatively short time the pipe-shaped flap opening becomes floppy and difficult to handle, sometimes stopping flow as a result.
Disposable packagings of the kind described above can, however, also be manufactured from other known packaging material which is completely free of paper and cardboarded layers or other layers of water-absorbent material. For example EP-A-O 353 991 and EP-A-O 353 496 describe a packaging material free of absorbent fibrous layers which is sufficiently flexible to let itself be shaped, through fold forming, into, for example, a packaging material of the Tetra Brik type. This known packaging material includes a stiffening skeletal layer of plastic and filler mixed into the plastic to an amount of between 50 and 80% of the total weight of the skeletal layer. The plastic in the skeletal layer is preferably a polyolefin plastic such as polythene, polypropylene etc. Preferably a polypropylene based plastic is used such as a propylene homopolymer with a melting index of under 10 according to ASTM (2.16 kg; 230.degree. C.) or an ethylene/propylene copolymer with a melting index of between 0.5 and 5 according to ASTM (2.16 kg; 230.degree. C.). Neither EP-A-O 353 991 nor EP-A-O 353 496, however, gives a single example of how a packaging of the described packaging material should be shaped to be easily opened and to be able to be emptied of its contents in the desired collected and well directed stream.